Imaging device, driving method, and electronic apparatus

ABSTRACT

The imaging device includes: a pixel region in which pixels are arranged, the pixels each including a photoelectric conversion unit that converts incident light into electric charges through electric conversion and stores the electric charges, and two or more charge storage units that store the electric charges transferred from the photoelectric conversion unit; and a drive unit that drives the pixels. The drive unit drives each pixel to cause the photoelectric conversion unit to repeatedly transfer electric charges with different exposure times to the two or more charge storage units during the light reception period of one frame. The present technology can be applied to an imaging device capable of capturing an HDR image, for example.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 15/546,496, filed Jul. 26, 2017, which is aNational Stage Entry PCT/JP2016/052592, filed Jan. 29, 2016, whichclaims priority from prior Japanese Priority Patent Application2015-026497 filed in the Japan Patent Office on Feb. 13, 2015, theentire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to an imaging device, a driving method,and an electronic apparatus, and more particularly, to an imagingdevice, a driving method, and an electronic apparatus that can capturean image with a higher dynamic range.

BACKGROUND ART

In a conventional electronic apparatus having an imaging function, suchas a digital still camera or a digital video camera, a solid-stateimaging device like a charge coupled device (CCD) or a complementarymetal oxide semiconductor (CMOS) image sensor is used. A solid-stateimaging device has pixels each including a combination of a photodiode(PD) that performs photoelectric conversion and transistors, and animage is formed in accordance with pixel signals that are output fromthe pixels arranged in a two-dimensional fashion. Further, the pixelsignals output from the pixels are subjected to AD conversion inparallel by analog-to-digital (AD) converters arranged for therespective columns of the pixels, for example, and the pixel signals arethen output.

Also, there have been various recently suggested techniques forcapturing a high dynamic range (HDR) image that has a dynamic rangewidened by an imaging method by which signals generated in differentexposure times are combined.

For example, Patent Document 1 discloses a solid-state imaging devicethat drives a pixel including first and second charge storage units sothat an electric charge equal to or smaller than the saturation chargeamount of the first charge storage unit is stored in the first chargestorage unit, and an electric charge exceeding the saturation chargeamount of the first charge storage unit is stored in the first andsecond charge storage units. With this imaging device, it is possible toincrease the HDR ratio while improving the signal-to-noise ratio (SNR),by performing HDR combining in three stages: low illuminance, mediumilluminance, and large illuminance.

CITATION LIST Patent Document

Patent Document 1: Japanese Patent No. 5521682

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

In the configuration disclosed in Patent Document 1, however, in a casewhere the installation area of the charge storage units is limited, thetotal capacity of electric charges that can be stored in the chargestorage units cannot be increased, and therefore, only the two separatecharge storage units are formed. Because of this, the dynamic rangeexpansion rate of each charge storage unit becomes lower. Therefore, theexpansion ratio in dynamic range cannot be improved, and it is difficultto capture an image with a higher dynamic range.

The present disclosure is made in view of those circumstances, and is toenable capturing of an image with a higher dynamic range.

Solutions to Problems

An imaging device according to one aspect of the present disclosureincludes: a pixel region in which pixels are arranged, the pixels eachincluding a photoelectric conversion unit that converts incident lightinto electric charges through electric conversion and stores theelectric charges, and two or more charge storage units that store theelectric charges transferred from the photoelectric conversion unit; anda drive unit that drives each pixel to cause the photoelectricconversion unit to repeatedly transfer electric charges with differentexposure times to the two or more charge storage units during the lightreception period of one frame.

A driving method according to one aspect of the present disclosure is amethod of driving an imaging device that includes: a pixel region inwhich pixels are arranged, the pixels each including a photoelectricconversion unit that converts incident light into electric chargesthrough electric conversion and stores the electric charges, and two ormore charge storage units that store the electric charges transferredfrom the photoelectric conversion unit; and a drive unit that drives thepixels. The method includes repeatedly transferring electric chargeswith different exposure times from the photoelectric conversion unit tothe two or more charge storage units during the light reception periodof one frame, the drive unit causing the photoelectric conversion unitto repeatedly transfer electric charges.

An electronic apparatus according to one aspect of the presentdisclosure includes an imaging device that includes: a pixel region inwhich pixels are arranged, the pixels each including a photoelectricconversion unit that converts incident light into electric chargesthrough electric conversion and stores the electric charges, and two ormore charge storage units that store the electric charges transferredfrom the photoelectric conversion unit; and a drive unit that driveseach pixel to cause the photoelectric conversion unit to repeatedlytransfer electric charges with different exposure times to the two ormore charge storage units during the light reception period of oneframe.

In one aspect of the present disclosure, electric charges with differentexposure times are repeatedly transferred from a photoelectricconversion unit to two or more electric charge storage units during thelight reception period of one frame.

Effects of the Invention

According to one aspect of the present disclosure, an image with ahigher dynamic range can be captured.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing an example configuration of anembodiment of an imaging device to which the present technology isapplied.

FIG. 2 is a circuit diagram showing a first configuration example of apixel.

FIG. 3 is a diagram showing a planar configuration example of the pixelof the first configuration example.

FIG. 4 is a diagram for explaining a method of driving an imaging deviceincluding pixels of the first configuration example.

FIG. 5 is a circuit diagram showing a second configuration example of apixel.

FIG. 6 is a diagram showing a planar configuration example of the pixelof the second configuration example.

FIG. 7 is a diagram for explaining a method of driving an imaging deviceincluding pixels of the second configuration example.

FIG. 8 is a circuit diagram showing a third configuration example of apixel.

FIG. 9 is a diagram showing a planar configuration example of the pixelof the third configuration example.

FIG. 10 is a circuit diagram showing a fourth configuration example of apixel.

FIG. 11 is a diagram showing a planar configuration example of the pixelof the fourth configuration example.

FIG. 12 is a diagram for explaining a method of driving an imagingdevice including pixels of the fourth configuration example.

FIG. 13 is a circuit diagram showing a fifth configuration example of apixel.

FIG. 14 is a diagram showing a planar configuration example of the pixelof the fifth configuration example.

FIG. 15 is a schematic perspective view of the configuration of a pixelprovided in a front-illuminated imaging device.

FIG. 16 is a schematic perspective view of the configuration of a pixelprovided in a back-illuminated imaging device.

FIG. 17 is a schematic perspective view of the configuration of a pixelprovided in a back-illuminated imaging device.

FIG. 18 is a diagram for explaining a first modification of the drivingmethod.

FIG. 19 is a diagram for explaining a second modification of the drivingmethod.

FIG. 20 is a block diagram showing an example configuration of anembodiment of an imaging apparatus to which the present technology isapplied.

MODES FOR CARRYING OUT THE INVENTION

The following is a detailed description of specific embodiments to whichthe present technology is applied, with reference to the drawings.

FIG. 1 is a block diagram showing an example configuration of anembodiment of an imaging device to which the present technology isapplied.

As shown in FIG. 1, an imaging device 1 includes a pixel region 2, avertical drive circuit 3, a column signal processing circuit 4, ahorizontal drive circuit 5, an output circuit 6, and a control circuit7.

The pixel region 2 is a light receiving surface for receiving lightcondensed by an optical system (not shown). In the pixel region 2,pixels 11 are arranged in a matrix fashion. The pixels 11 are connectedto the vertical drive circuit 3 via horizontal signal lines row by row,and are also connected to the column signal processing circuit 4 viavertical signal lines column by column. The pixels 11 each output apixel signal at the level corresponding to the amount of received light,and an image of the object to be formed in the pixel region 2 is formedfrom these pixel signals.

For each row of the pixels 11 arranged in the pixel region 2, thevertical drive circuit 3 sequentially supplies drive signals for driving(or transferring signals to, selecting, resetting, or the like) therespective pixels 11, to the pixels 11 via the horizontal signal lines.

The column signal processing circuit 4 conduct AD conversion on an imagesignal and removes reset noise by performing correlated double sampling(CDS) on the pixel signals output from the respective pixels 11 via thevertical signal lines.

For each column of the pixels 11 arranged in the pixel region 2, thehorizontal drive circuit 5 sequentially supplies drive signals foroutputting the pixel signals from the column signal processing circuit 4to data output signal lines, to the column signal processing circuit 4.

The output circuit 6 amplifies pixel signals supplied from the columnsignal processing circuits 4 at the times in accordance with the drivesignals from the horizontal drive circuit 5 via the data output signallines, and outputs the amplified pixel signals to a signal processingcircuit in a later stage.

The control circuit 7 controls driving of the respective blocks in theimaging device 1. For example, the control circuit 7 generates clocksignals in accordance with the drive cycles of the respective blocks,and supplies the clock signals to the respective blocks.

In the imaging device 1 having the above configuration, each pixel 11 isdesigned to include charge storage units so that a moving image as anHDR image can be captured, and electric charges of different exposuretimes are stored in the charge storage units.

Referring now to FIGS. 2 to 4, a first configuration example of a pixel11 and a driving method are described.

FIG. 2 is a circuit diagram showing the first configuration example of apixel 11.

As shown in FIG. 2, a pixel 11 is designed to include a PD 21, chargereadout paths 22-1 to 22-3, and an anti-blooming gate 23.

The PD 21 is a photoelectric conversion unit that converts incidentlight into an electric charge through photoelectric conversion, andstores the electric charge. The anode terminal of the PD 21 is grounded,and the cathode terminal of the PD 21 is connected to the verticalsignal line via the charge readout paths 22-1 to 22-3, and is alsoconnected to the drain via the anti-blooming gate 23.

The charge readout path 22-1 includes a transfer gate 31-1, a chargestorage gate 32-1, a readout gate 33-1, an FD unit 34-1, a storagecapacitor 35-1, an amplification transistor 36-1, a select transistor37-1, and a reset transistor 38-1. It should be noted that the chargereadout paths 22-2 and 22-3 each have a configuration similar to that ofthe charge readout path 22-1, and therefore, detailed explanationthereof is not made herein.

The gate electrode of the transfer gate 31-1 and the gate electrode ofthe charge storage gate 32-1 are connected, and the transfer gate 31-1and the charge storage gate 32-1 are driven at the same time inaccordance with a transfer pulse FSG1/STG1 applied to the gateelectrodes. That is, at a time when the transfer pulse FSG1/STG1switches to “on”, the electric charge stored in the PD 21 is transferredto the charge storage gate 32-1 via the transfer gate 31-1, and isstored in the charge storage gate 32-1.

The readout gate 33-1 is driven in accordance with a readout pulse ROG1applied to the gate electrode, and at a time when the readout pulse ROG1switches to “on”, the electric charge stored in the charge storage gate32-1 is read and output to the FD unit 34-1.

The FD unit 34-1 is a floating diffusion region having the predeterminedstorage capacitor 35-1 connected to the gate electrode of theamplification transistor 36-1, and temporarily stores the electriccharge transferred via the readout gate 33-1 into the storage capacitor35-1.

The amplification transistor 36-1 outputs a pixel signal at the levelcorresponding to the electric charge stored in the storage capacitor35-1 of the FD unit 34-1 (or the potential of the FD unit 34-1), to thevertical signal line via the select transistor 37-1. That is, the FDunit 34-1 is connected to the gate electrode of the amplificationtransistor 36-1, so that the FD unit 34-1 functions as a charge-voltageconversion unit that converts the electric charge transferred from thePD 21 to the charge storage gate 32-1, into a pixel signal at the levelcorresponding to the electric charge.

The select transistor 37-1 is driven by a select signal SEL1 suppliedfrom the vertical drive circuit 3. When the select transistor 37-1 isswitched on, the pixel signal to be output from the amplificationtransistor 36-1 can be output to the vertical signal line.

The reset transistor 38-1 is driven by a reset signal RG1 supplied fromthe vertical drive circuit 3. When the reset transistor 38-1 is switchedon, the electric charge stored in the storage capacitor 35-1 of the FDunit 34-1 is discharged to the drain. As a result, the storage capacitor35-1 of the FD unit 34-1 is reset.

The charge readout path 22-1 has the above configuration, and a pixelsignal corresponding to the electric charge transferred from the PD 21to the charge storage gate 32-1 is read out via the charge readout path22-1. Likewise, in the charge readout path 22-2, a pixel signalcorresponding to the electric charge transferred from the PD 21 to thecharge storage gate 32-2 is read out. In the charge readout path 22-3, apixel signal corresponding to the electric charge transferred from thePD21 to the charge storage gate 32-3 is read out.

The anti-blooming gate 23 is driven in accordance with a discharge pulseABG applied to the gate electrode, and, at a time when the dischargepulse ABG switches to “on”, the electric charge stored in the PD 21 isdischarged to the drain. In this manner, shutter control is performed.Further, the potential of the anti-blooming gate 23 is set so thatelectric charge overflows from the PD 21 via the anti-blooming gate 23in a case where extremely intense light enters the PD 21.

The pixel 11 designed as above can read out the electric chargegenerated in the PD 21 via the charge readout paths 22-1 to 22-3, inaccordance with driving of the vertical drive circuit 3 shown in FIG. 1.Accordingly, during the light reception period of one frame, the pixel11 can sequentially transfer the electric charge in the PD 21 to thecharge storage gate 32-1, the charge storage gate 32-2, and the chargestorage gate 32-3, and thus, store electric charges (pixel signals) ofthree different exposure times. Further, by such a driving method, theimaging device 1 can obtain pixel signals of different exposure timesfrom one another.

For example, the imaging device 1 drives the pixel 11 by such a drivingmethod that an electric charge with a short storage time (hereinafterreferred to as short storage, where appropriate) is transferred to thecharge storage gate 32-1, an electric charge with a medium storage time(hereinafter referred to as medium storage, where appropriate) istransferred to the charge storage gate 32-2, and an electric charge witha long storage time (hereinafter referred to as long storage, whereappropriate) is transferred to the charge storage gate 32-3. In thisoperation, driving is performed so that the timing of supplying thetransfer pulse FSG/STG for transferring an electric charge is set to aperiod sufficiently shorter than one frame, and charge transfer to thecharge storage gate 32-1, the charge storage gate 32-2, and the chargestorage gate 32-3 is repeatedly performed (this driving method will behereinafter referred to as the burst distribution driving, whereappropriate).

Further, in the imaging device 1, after the electric charges of oneframe are stored, the pixel signals corresponding to the electriccharges transferred to the charge storage gate 32-1, the charge storagegate 32-2, and the charge storage gate 32-3 are read out, and HDRcombining is performed. As a result, an HDR image with a sufficientlywide dynamic range can be obtained. For example, the exposure ratiosamong the electric charges to be transferred to the charge storage gate32-1, the charge storage gate 32-2, and the charge storage gate 32-3 areset to 1 (60 dB):32(+30 dB):1000(+30 dB), so that the imaging device 1can obtain an HDR image of 120 dB.

The exposure ratios among the electric charges to be transferred to thecharge storage gate 32-1, the charge storage gate 32-2, and the chargestorage gate 32-3 are now described.

For example, in the imaging device 1, it is necessary to maintain 120 dBin order to cover the light range from moonlight to sunlight. As thesize of the imaging device 1 has been becoming smaller and smaller thesedays, the saturation charge amounts of the PD 21, the charge storagegate 32, and the like are less than 10,000 electrons. Meanwhile, severalelectrons of dark current and circuit noise remain within the actualoperation temperature range, and the dynamic range of one PD 21 or onecharge storage gate 32 is approximately 20 LOG (10000 e/10e)=approximately 60 dB, for example.

Further, in a case where HDR combining is performed with images havingsensitivity differences, if a high-illuminance image is to be generatedat a noise level of several electrons, the SNR difference becomes toowide at the portion to be combined with a high-SNR image having alow-saturation signal on the low-illuminance side, resulting in imagedestruction.

Therefore, among signals on the high-illuminance side, only signalsequal to or higher than a certain SNR can be normally used in HDRcombining. For example, where the visually acceptable level is about 20dB, the amount that can be used in expanding the dynamic range on thehigh-illuminance side is +40 dB, instead of +60 dB. Therefore, aDR=(60+40)=100 dB is achieved with two signals, and, with such a DR, itis not possible to achieve 120 dB to cover the light range frommoonlight to sunlight.

In view of this, three charge storage gates 32-1 to 32-3 are used in theimaging device 1, to set a DR at (60+40+40)=140 dB. Thus, the goal tocover the light range from moonlight to sunlight can be achieved.

Next, FIG. 3 shows an example planar configuration of the pixel 11 shownin FIG. 2.

As shown in FIG. 3, in the pixel 11, the charge readout paths 22-1 to22-3 are designed to be connected to three sides of the PD 21 formed ina substantially square shape, and the anti-blooming gate 23 is designedto be connected to the remaining one side of the PD 21.

In the charge readout path 22-1, the transfer gate 31-1, the chargestorage gate 32-1, the readout gate 33-1, and the reset transistor 38-1are arranged in order from the PD 21 side. It should be noted that thecharge readout paths 22-2 and 22-3 each have a configuration similar tothat of the charge readout path 22-1, and therefore, detailedexplanation thereof is not made herein. Also, in FIG. 3, theamplification transistor 36 and the select transistor 37 are not shown.

The transfer gate 31-1 and the charge storage gate 32-1 are designed tohave a common gate electrode 41-1, and the gate electrode 41-1 isdisposed adjacent to the PD 21. Also, a through electrode 44-1 connectedto the FD unit 34 is disposed between a gate electrode 42-1 forming thereadout gate 33-1 and a gate electrode 43-1 forming the reset transistor38-1. Further, a through electrode 45-1 connected to the drain of thereset transistor 38-1 is disposed on the opposite side of the gateelectrode 43-1 from the through electrode 44-1.

In the anti-blooming gate 23, a gate electrode 51-1 is disposed adjacentto the PD 21, and a through electrode 52 connected to the drain isdisposed on the opposite side of the gate electrode 51-1 from the PD 21.

Meanwhile, on the light receiving surface side of the pixel 11, a lightshielding film 61 is formed to shield light from the charge readoutpaths 22-1 to 22-3 and the anti-blooming gate 23. The light shieldingfilm 61 is provided with an opening 62 for guiding light into the PD 21.

As described above, the pixel 11 is designed so that the charge readoutpaths 22-1 to 22-3 are arranged in three directions (a 3-tap structure),and the anti-blooming gate 23 is arranged in the remaining onedirection. With such a configuration, the pixel 11 can read electriccharges of different exposure times via the charge readout paths 22-1 to22-3, as described above.

It should be noted that, as shown in FIGS. 2 and 3, the pixel 11 employsthe charge storage gates 32-1 to 32-3 each having a buried-channel-typestructure provided with a gate electrode as the charge storage unitsthat store electric charges transferred from the PD 21. Moreover, thepixel 11 can employ charge storage units of various structure types,such as a floating diffusion type or a buried-channel type provided witha virtual gate. In such a case, the capacity of these charge storageunits can be set in accordance with the dynamic range ratio or the SNR.Also, as the dynamic range of the pixel 11 can be widened, the pixel 11may not include the anti-blooming gate 23. Further, it is possible toemploy a FD sharing structure that has been widely used forminiaturization in recent years. In such a structure, an FD unit 34 andthe circuits in the later stages can be shared. Specifically, the FDunit 34-1, the FD unit 34-2, and the FD unit 34-3 are connected to formone FD unit, and the FD unit is shared among a reset transistor 38, anamplification transistor 36, a select transistor 37, and charge readoutpaths 22-1 to 22-3. Such a structure can also be employed.

Referring now to FIG. 4, a method of driving the imaging device 1 isdescribed.

For example, where the frame rate at which the imaging device 1 capturesa moving image is 60 fps, the exposure time per frame is 16.7 ms. Then,after finishing imaging of one frame, the imaging device 1 sequentiallyperforms rolling shutter reading row by row.

In the example shown in FIG. 4, electric charges are transferred fromthe PD 21 in the following order: long storage transfer to the chargestorage gate 32-3, short storage transfer to the charge storage gate32-1, and medium storage transfer to the charge storage gate 32-2. Then,in the imaging device 1, the charge exposure time per charge transferoperation to be performed multiple times for the charge storage gate32-3, the charge storage gate 32-1, and the charge storage gate 32-2 isset at a sufficiently shorter time than the exposure time of one frame,and long storage transfer, short storage transfer, and medium storagetransfer are repeatedly performed in one frame. Here, the exposure timesfor the long storage, the short storage, and the medium storage to betransferred to the charge storage gate 32-3, the charge storage gate32-1, and the charge storage gate 32-2, respectively, are substantiallyconstant in each of the charge storage gate 32-3, the charge storagegate 32-1, and the charge storage gate 32-2.

First, as shown in the drawing, exposure for the long storage is startedat the time when the discharge pulse ABG switches to “on” at time t1,and the electric charges stored in the PD 21 are discharged via theanti-blooming gate 23. Then, at time t2, the transfer pulse FSG3switches to “on”, and the long storage is transferred from the PD 21 tothe charge storage gate 32-3 and is stored therein.

After that, at time t3, the discharge pulse ABG switches to “on”, andexposure for the short storage is started. At time t4, the transferpulse FSG1 switches to “on”, and the short storage is transferred fromthe PD 21 to the charge storage gate 32-1 and is stored therein.

Subsequently, at time t5, the discharge pulse ABG switches to “on”, andexposure for the medium storage is started. At time t6, the transferpulse FSG2 switches to “on”, and the medium storage is transferred fromthe PD 21 to the charge storage gate 32-2 and is stored therein.

Thereafter, such transfer of the long storage, the short storage, andthe medium storage between time t1 and time t6 is repeatedly performedin a similar manner during one frame. For example, where the ratio amongthe exposure times for the short storage, the medium storage, and thelong storage is set at 5 ns:0.5 μs:50 μs=1:100:10000, the imaging device1 can obtain an HDR image with (40+40) dB.

It should be noted that FIG. 4 shows an example where imaging isperformed with a sensitivity of ½ of the maximum sensitivity of thepixel 11.

For example, the exposure time for the long storage (the period fromtime t1 to time t2) is determined by setting time t1 within the periodfrom the time when the transfer pulse FSG2 switches to “on” immediatelybefore time t1, to the time when the transfer pulse FSG3 switches to“on” at time t2. In a case where the exposure time for the long storageis the maximum (maximum sensitivity), time t1 should be set at the sametime as the time when the transfer pulse FSG2 switches to “on”immediately before that, and exposure for the long storage should bethen started. In the example shown in FIG. 4, time t1 is set at such atime that the period becomes ½. Alternatively, to maximize the exposuretime, all the discharge driving for the discharge pulse ABG may beturned off.

Likewise, in the example shown in FIG. 4, as for the exposure time forthe short storage (the period from time t3 to time t4), time t3 is setat such a time that the period from time t2 to time t4 becomes ½. Also,as for the exposure time for the medium storage (the period from time t5to time t6), time t5 is set at such a time that the period from time t4to time t6 becomes ½. Further, the transfer pulses FSG1 to FSG3 and thedischarge pulse ABG are set so as to be synchronized with one line inthe rolling shutter reading. In this manner, the synchronous circuitdesign can be simplified.

By the driving method described above, the imaging device 1 can generatethree images with different exposure times and perform HDR combining,simply by controlling the timing of transferring electric charges in thepixels 11. In doing so, for example, the imaging device 1 can performthe combining even if the amount of the electric charge in the shortstorage is small, and improve the SNR in the stage of the HDR combining.Thus, the imaging device 1 can obtain an HDR image with less noise.

As described above, the imaging device 1 is designed to include two ormore charge storage gates for the single PD 21, and include the threecharge storage gates 32-1 to 32-3 in the configuration example shown inFIG. 2. The imaging device 1 also performs burst distribution driving,to control the exposure time ratio in an HDR image. As described above,by distributing the transfer of electric charges to the charge storagegates 32-1 to 32-3 in a time-division manner, the imaging device 1 cancertainly capture an image with a high dynamic range.

Further, as the imaging device 1 has a structure using the single PD 21,sensitivity loss can be reduced. Accordingly, the SNR at a lowilluminance can be improved, while a high dynamic range is achieved.Thus, an HDR image of higher image quality can be captured.

Referring now to FIGS. 5 to 7, a second configuration example of a pixel11 and a driving method are described.

FIG. 5 shows a circuit diagram of a pixel 11A as the secondconfiguration example. FIG. 6 shows a planar configuration example ofthe pixel 11A.

As shown in FIGS. 5 and 6, the pixel 11A includes a PD 21, chargereadout paths 22-1A and 22-2A, and an anti-blooming gate 23. It shouldbe noted that the PD 21, the charge readout path 22-1A, and theanti-blooming gate 23 have configurations similar to those of the pixel11 shown in FIG. 2, and therefore, detailed explanation thereof is notmade herein.

That is, while the pixel 11 in FIG. 2 has the three charge readout paths22-1 to 22-3, the pixel 11A has the two charge readout paths 22-1A and22-2A, and the configuration of the charge storage path 22-2A differsfrom that of the corresponding charge storage path of the pixel 11 inFIG. 2.

The charge readout path 22-2A includes a transfer gate 31-2, a capacitor71, a readout gate 33-2, an FD unit 34-2, a storage capacitor 35-2, anamplification transistor 36-2, a select transistor 37-2, and a resettransistor 38-2. As described above, the charge readout path 22-2Adiffers from the charge readout path 22-2 in FIG. 2 in that the chargestorage gate 32-2 is replaced with the capacitor 71 that extends througha diffusion junction and is connected via a through electrode 46-2.

In the pixel 11A having such a configuration, an electric charge in thePD 21 is transferred to the capacitor 71 via the transfer gate 31-2, andis stored therein. That is, the pixel 11A is designed to employ acapacitor-type charge storage unit, instead of a buried-channel-typecharge storage unit, as the charge storage unit in the charge readoutpath 22-2A.

With this configuration, the pixel 11A can make the storage capacity ofthe capacitor 71 in the charge readout path 22-2A larger than that ofthe charge storage gate 32-2 in the charge readout path 22-2 in FIG. 2.Accordingly, by transferring the long storage to the charge storage gate32-1, the pixel 11A can achieve a high SNR from a low illuminance.Furthermore, by transferring the short storage to the capacitor 71, thepixel 11A can prevent electric charges from overflowing even in the caseof a high-luminance object, such as the sun. That is, in the pixel 11A,the capacitor 71 and the charge storage gate 32-2 are designed so thatthe possible charge storage capacities differ from each other, the longstorage is transferred to the charge storage gate 32-2 having thesmaller charge storage capacity, and the short storage is transferred tothe capacitor 71 having the larger charge storage capacity.

For example, the storage capacity of the capacitor 71 is set at a value(60+20 dB) 10 or more times greater than the storage capacity (60 dB) ofthe charge storage gate 32-1, and the storage time difference betweenthe two is set at 1:1000 (+60 dB). In this manner, an HDR image with(60+60)=120 dB can be generated while 20 dB is maintained during the HDRcombining.

Thus, an imaging device 1 including such a pixel 11A can capture an HDRimage having a sufficient dynamic range, even though the pixel 11A has astructure including the two charge readout paths 22-1A and 22-2A (2-tapstructure). Furthermore, the pixel 11A has a simpler configuration thanthe pixel 11, and the imaging device 1 including the pixel 11A has astructure advantageous for miniaturization, for example.

It should be noted that, other than the structure shown in the drawings,the pixel 11A can employ a charge storage unit having any appropriatestructure, such as a structure of a floating diffusion type or aburied-channel type with a virtual gate. In such a case, the capacitiesof these charge storage units can be set at different values inaccordance with the dynamic range ratio and the SNR.

Referring now to FIG. 7, a method of driving the imaging device 1including the pixel 11A is described.

In the example shown in FIG. 7, electric charges are transferred fromthe PD 21 in the following order: the long storage to the charge storagegate 32-1, and the short storage to the capacitor 71. Then, the chargeexposure time per charge transfer operation to be performed multipletimes for the charge storage gate 32-1 and the capacitor 71 is set at asufficiently shorter time than the exposure time of one frame, and longstorage transfer and short storage transfer are repeatedly performed inone frame.

First, as shown in the drawing, exposure for the long storage is startedat the time when the discharge pulse ABG switches to “on” at time t1,and the electric charges stored in the PD 21 are discharged via theanti-blooming gate 23. Then, at time t2, the transfer pulse FSG1switches to “on”, and the long storage is transferred from the PD 21 tothe charge storage gate 32-1.

After that, at time t3, the discharge pulse ABG switches to “on”, andexposure for the short storage is started. At time t4, the transferpulse FSG2 switches to “on”, and the short storage is transferred fromthe PD 21 to the capacitor 71.

Thereafter, such transfer of the long storage and the short storagebetween time t1 and time t4 is repeatedly performed in a similar mannerduring one frame. For example, where the ratio between the exposuretimes for the short storage and the long storage is set at 0.5 μs:50μs=1:100, the imaging device 1 can obtain an HDR image with +40 dB.

It should be noted that, like FIG. 4, FIG. 7 shows an example whereimaging is performed with a sensitivity of ½ of the maximum sensitivityof the pixel 11A. Further, the transfer pulses FSG1 to FSG3 and thedischarge pulse ABG are set so as to be synchronized with one line inthe rolling shutter reading. In this manner, the synchronous circuitdesign can be simplified.

By the above driving method, the imaging device 1 can achieve both ahigh SNR at a time of low illuminance and a resistance to highluminance. Furthermore, by virtue of the burst distribution driving inwhich exposure of a sufficiently shorter time than one frame isrepeatedly performed, it is possible to image a pulsed light emissionsource, such as an LED light source, even on the short storage side.Power consumption can also be reduced.

Referring now to FIGS. 8 and 9, a third configuration example of a pixel11 is described.

FIG. 8 shows a circuit diagram of a pixel 11B as the third configurationexample. FIG. 9 shows a planar configuration example of the pixel 11B.

As shown in FIGS. 8 and 9, the pixel 11B includes a PD 21, a chargereadout path 22-1B, a charge readout path 22-2B, and an anti-bloominggate 23. It should be noted that the PD 21 and the anti-blooming gate 23have configurations similar to those of the pixel 11 shown in FIG. 2,and therefore, detailed explanation thereof is not made herein.Meanwhile, the charge readout path 22-2B has a configuration similar tothat of the charge readout path 22-2A shown in FIG. 5.

That is, in the pixel 11B, the structure of the charge readout path22-1B differs from that of the charge readout path 22-1A shown in FIG.5.

The charge readout path 22-1B includes a transfer gate 31-1, alight-shielded hole accumulation diode (HAD) 72, a readout gate 33-1, anFD unit 34-1, a storage capacitor 35-1, an amplification transistor36-1, a select transistor 37-1, and a reset transistor 38-1. Asdescribed above, the charge readout path 22-1B differs from the chargereadout path 22-1A in FIG. 5 in that the charge storage gate 32-1 isreplaced with the light-shielded HAD 72 with low noise.

In the pixel 11B having such a configuration, an electric charge in thePD 21 is transferred to the light-shielded HAD 72 via the transfer gate31-1, and is stored therein. That is, the pixel 11B is designed toemploy a photodiode structure of a light-shielded HAD type, instead of aburied-channel-type charge storage unit, as the charge storage unit inthe charge readout path 22-1B. It should be noted that the differencebetween the structure of the light-shielded HAD 72 and the structure ofthe PD 21 is only that the light-shielded HAD 72 is shielded by a lightshielding film 61B while the PD 21 is not shielded from light.Accordingly, the light-shielded HAD 72 used as a charge storage unit canalso achieve a SNR similar to that to be achieved by the PD 21.

Thus, the pixel 11B can achieve a high SNR from a low illuminance, bytransferring the long storage to the light-shielded HAD 72. Furthermore,by transferring the short storage to the capacitor 71, the pixel 11B,like the pixel 11A, can prevent electric charges from overflowing evenin the case of a high-luminance object, such as the sun.

Also, an imaging device 1 including the pixel 11B can be driven by adriving method similar to the method of driving the imaging device 1having the pixel 11A as described above with reference to FIG. 7. Thus,the imaging device 1 can achieve both a high SNR at a time of lowilluminance and a resistance to high luminance.

Accordingly, like the imaging device 1 including the above describedpixel 11A, the imaging device 1 including such a pixel 11B can capturean HDR image having a sufficient dynamic range, even though the pixel11B has a structure including the two charge readout paths 22-1B and22-2B (2-tap structure). Furthermore, the pixel 11B has a simplerconfiguration than the pixel 11, and the imaging device 1 including thepixel 11B has a structure advantageous for miniaturization, for example.

Referring now to FIGS. 10 to 12, a fourth configuration example of apixel 11 and a driving method are described.

FIG. 10 shows a circuit diagram of a pixel 11C as the fourthconfiguration example. FIG. 11 shows a planar configuration example ofthe pixel 11C. As shown in FIGS. 10 and 11, the pixel 11C includes a PD21, a charge readout path 22-1C, and a charge readout path 22-2C.

The pixel 11C differs from the pixel 11A shown in FIG. 5, for example,in that the anti-blooming gate 23 is not provided, and the chargereadout path 22-1C and the charge readout path 22-2C share somecomponents.

For example, the ratio (HDR ratio) between the charge storage gate 32-1and the capacitor 71 is set at such a ratio that electric charges do notoverflow even in the case of a high-luminance object, such as the sun.In this manner, the anti-blooming gate 23 can be made unnecessary. Inview of this, the pixel 11C does not include the anti-blooming gate 23.

It should be noted that the bias of the transfer gate 31-1 is set sothat the electric charges first overflow toward the side of the chargereadout path 22-1C in a case where electric charges overflow from the PD21. That is, the potential is set so that electric charges overflowingfrom the PD 21 are discharged to the charge storage gate 32-1 having asmaller charge storage capacity than the capacitor 71. In a case whereelectric charges overflow from the PD 21 in this manner, it is possibleto form an image using only the electric charges read from the side ofthe charge readout path 22-2C.

Further, the pixel 11C is designed so that an FD unit 34, a storagecapacitor 35, an amplification transistor 36, a select transistor 37,and a reset transistor 38 are shared between the charge readout path22-1C and the charge readout path 22-2C. In such a configuration inwhich the charge readout path 22-1C and the charge readout path 22-2Cshare the FD unit 34 and the components in the later stages as describedabove, control is performed so that the respective electric charges areread as pixel signals at different times. Further, the configuration inwhich the charge readout path 22-1C and the charge readout path 22-2Cshare the FD unit 34 and the components in the later stages can beformed simply by adding a readout gate 33-2 to a conventional globalshutter pixel, for example.

Further, in the pixel 11C, the capacitor 71 may be disposed in a regionindicated by a dot-and-dash line in FIG. 11. That is, in the pixel 11C,the capacitor 71 is positioned so as to overlap the transfer gate 31-1and the gate electrode 41-1 of the charge storage gate 32-1, and thus,the planar layout is effectively used. In this manner, the capacity ofthe capacitor 71 can be maintained.

The pixel 11C having such a configuration is simpler than the pixel 11and the pixels 11A and 11B, and accordingly, can be made smaller insize. An imaging device 1 including the pixel 11C is remarkablyadvantageous for miniaturization, for example.

It should be noted that, in a use case where shutter control isnecessary, it is preferable to provide the anti-blooming gate 23 (seeFIG. 2) in the pixel 11C, and an appropriate configuration can beemployed in accordance with the purpose of use.

It should be noted that, other than the structure shown in the drawings,the pixel 11C can also employ a charge storage unit having anyappropriate structure, such as a structure of a floating diffusion typeor a buried-channel type with a virtual gate. In such a case, thecapacities of these charge storage units can be set at different valuesin accordance with the dynamic range ratio and the SNR.

Referring now to FIG. 12, a method of driving the imaging device 1including the pixel 11C is described. It should be noted that FIG. 12illustrates a driving method to be implemented in a case where the pixel11C includes the anti-blooming gate 23, and shutter control isperformed.

In the example shown in FIG. 12, electric charges are transferred fromthe PD 21 in the following order: the long storage to the charge storagegate 32-1, and the short storage to the capacitor 71. Then, the chargeexposure time per charge transfer operation to be performed multipletimes for the charge storage gate 32-1 and the capacitor 71 is set at asufficiently shorter time than the exposure time of one frame, and longstorage transfer and short storage transfer are repeatedly performed inone frame.

First, as shown in the drawing, exposure for the long storage is startedat the time when the discharge pulse ABG switches to “on” at time t1,and the electric charges stored in the PD 21 are discharged via theanti-blooming gate 23. Then, at time t2, the transfer pulse FSG1switches to “on”, and the long storage is transferred from the PD 21 tothe charge storage gate 32-1.

After that, at time t3, the discharge pulse ABG switches to “on”, andexposure for the short storage is started. At time t4, the transferpulse FSG2 switches to “on”, and the short storage is transferred fromthe PD 21 to the capacitor 71.

Thereafter, such transfer of the long storage and the short storagebetween time t1 and time t4 is repeatedly performed in a similar mannerduring one frame. For example, where the ratio between the exposuretimes for the short storage and the long storage is set at 0.5 μs:50μs=1:100, the imaging device 1 can obtain an HDR image with +40 dB.

It should be noted that, like FIG. 4, FIG. 12 shows an example whereimaging is performed with a sensitivity of ½ of the maximum sensitivityof the pixel 11A. Further, the transfer pulses FSG1 and FSG2, and thedischarge pulse ABG are set so as to be synchronized with one line inthe rolling shutter reading. In this manner, the synchronous circuitdesign can be simplified. It should be noted that, in a structurewithout the anti-blooming gate 23 as shown in FIG. 10 and FIG. 11, thedischarge pulse ABG shown in FIG. 12 is not used for driving, and amaximum sensitivity state is always maintained.

By the above driving method, the imaging device 1 can achieve both ahigh SNR at a time of low illuminance and a resistance to highluminance. Furthermore, by virtue of the burst distribution driving inwhich exposure of a sufficiently shorter time than one frame isrepeatedly performed, it is possible to image a pulsed light emissionsource, such as an LED light source, even on the short storage side.

Referring now to FIGS. 13 and 14, a fifth configuration example of apixel 11 is described.

FIG. 13 shows a circuit diagram of a pixel 11D as the fifthconfiguration example. FIG. 14 shows a planar configuration example ofthe pixel 11D.

As shown in FIGS. 13 and 14, the pixel 11D includes a PD 21, a chargereadout path 22-1D, and a charge readout path 22-2D. Meanwhile, thecharge readout path 22-2D has a configuration similar to that of thecharge readout path 22-2C shown in FIG. 10.

That is, in the pixel 11D, the structure of the charge readout path22-1D differs from that of the charge readout path 22-1C shown in FIG.10.

The charge readout path 22-1D includes a transfer gate 31-1, alight-shielded HAD 72, a readout gate 33-1, an FD unit 34-1, a storagecapacitor 35-1, an amplification transistor 36-1, a select transistor37-1, and a reset transistor 38-1. As described above, the chargereadout path 22-1D differs from the charge readout path 22-1C in FIG. 10in that the charge storage gate 32-1 is replaced with the light-shieldedHAD 72.

In the pixel 11D having such a configuration, an electric charge in thePD 21 is transferred to the light-shielded HAD 72 via the transfer gate31-1, and is stored therein. That is, the pixel 11D is designed toemploy a photodiode structure of a light-shielded HAD type, instead of aburied-channel-type charge storage unit, as the charge storage unit inthe charge readout path 22-1D.

Thus, the pixel 11D can achieve a high SNR from a low illuminance, bytransferring the long storage to the light-shielded HAD 72. Furthermore,by transferring the short storage to the capacitor 71, the pixel 11D,like the pixel 11C, can prevent electric charges from overflowing evenin the case of a high-luminance object, such as the sun.

Also, an imaging device 1 including the pixel 11D can be driven by adriving method similar to the method of driving the imaging device 1having the pixel 11C as described above with reference to FIG. 12. Thus,the imaging device 1 can achieve both a high SNR at a time of lowilluminance and a resistance to high luminance.

Accordingly, like the imaging device 1 including the above describedpixel 11C, the imaging device 1 including such a pixel 11D can capturean HDR image having a sufficient dynamic range, even though the pixel11D has a structure including the two charge readout paths 22-1D and22-2D (2-tap structure). Furthermore, like the imaging device 1including the pixel 11C, the imaging device 1 including the pixel 11D isremarkably advantageous for miniaturization, for example.

Also, in the pixel 11D, the capacitor 71 may be disposed in a regionindicated by a dot-and-dash line in FIG. 14. In this manner, the pixel11D can maintain the capacity of the capacitor 71, like the pixel 11Cshown in FIG. 11. It should be noted that, in the pixels 11C and 11D,adjacent pixels may share the FD unit 34 and the components in the laterstages.

Referring now to FIGS. 15 to 17, three-dimensional configurationexamples of pixels 11 are described.

An imaging device 1 is of one of the two types: a front-illuminated typein which a semiconductor substrate having a PD 21 formed therein isirradiated with light from the side of the front surface on which awiring layer and the like are stacked; and a back-illuminated type inwhich the front surface is irradiated with light from the side of theback surface located on the opposite side from the front surface, forexample. FIG. 15 shows a configuration example of a pixel 11E of afront-illuminated imaging device 1. FIGS. 16 and 17 show configurationexamples of a pixel 11F and a pixel 11G of a back-illuminated imagingdevice 1, respectively. Also, the pixels 11E to 11G shown in FIGS. 15 to17 each have a structure (3-tap structure) in which charge storage unitsare arranged in three directions with respect to the PD 21, as in thepixel 11 shown in FIG. 2.

FIG. 15 shows a schematic perspective view of the configuration of apixel 11E provided in a front-illuminated imaging device 1.

An on-chip lens 81 is provided on each pixel 11E. Light that enters viathe on-chip lens 81 passes through an opening in a light shielding film61 stacked on the wiring layer side of a semiconductor substrate havinga PD 21 provided therein, and irradiates the PD 21.

As shown in the drawing, charge storage units 82-1 to 82-3 are providedin three directions with respect to the PD 21, and a reset drain 83 isprovided in the remaining one direction. The charge storage units 82-1to 82-3 are equivalent to the charge storage gates 32-1 to 32-3 (seeFIG. 2), for example, and electric charges are transferred from the PD21 to the charge storage units 82-1 to 82-3 by the driving methoddescribed above with reference to FIG. 4. The reset drain 83 is used todischarge the electric charges in the PD 21 via the anti-blooming gate23 (see FIG. 2).

It should be noted that, in a case where the pixel 11E includes acapacitor 71 (see FIG. 5) in place of the charge storage unit 82-1 inthe configuration example in FIG. 15, the capacitor 71 is disposed in awiring layer provided between the semiconductor substrate having the PD21 formed therein and the light shielding film 61.

As described above, in the pixel 11E provided in the front-illuminatedimaging device 1, the PD 21 and the charge storage units 82-1 to 82-3are arranged in the same plane.

FIG. 16 shows a schematic perspective view of the configuration of apixel 11F provided in a back-illuminated imaging device 1.

An on-chip lens 81 is provided on each pixel 11F, and light that entersvia the on-chip lens 81 is applied to a PD 21. A light shielding film 61is stacked on the front surface side of the PD 21 (the side of thesurface facing downward in FIG. 16), and the light shielding film 61shields charge storage units 82-1 to 82-3 and a reset drain 83 fromlight.

As shown in the drawing, the charge storage units 82-1 to 82-3 and thereset drain 83 are disposed on the front surface side of thesemiconductor substrate having the PD 21 provided on its back side, soas to overlap the PD 21 when seen in a plan view. As described above,the PD 21 and the charge storage units 82-1 to 82-3 are not arranged inthe same plane in the pixel 11F provided in the back-illuminated imagingdevice 1. Accordingly, the charge storage units 82-1 to 82-3 can bedesigned to have larger areas than those in the pixel 11E shown in FIG.15.

In this manner, the size of the entire pixel 11F can be reduced, forexample. That is, most of the back surface side can be used for thecharge storage units 82-1 to 82-3, and the pixel 11F can be made smalleraccordingly. Furthermore, as the aperture ratio of the PD 21 can beincreased without being affected by the charge storage units 82-1 to82-3, photosensitivity can be increased.

FIG. 17 shows a schematic perspective view of the configuration of apixel 11G provided in a back-illuminated imaging device 1.

As shown in FIG. 17, the pixel 11G is formed by adding a capacitor 71 tothe structure of the pixel 11F shown in FIG. 16. For example, in thepixel 11E included in the back-illuminated imaging device 1 in FIG. 15,the capacitor 71 can be disposed only below the light shielding film 61(that is, the capacitor 71 cannot be placed in the opening), whichrestricts the capacity of the capacitor 71 to a small value.

In the pixel 11G, on the other hand, there is no such restriction, andthe entire region of the pixel 11G can be used for the capacitor 71.Accordingly, the area and the capacity of the capacitor 71 can be madelarger in the pixel 11G, without affecting the photosensitivity of thePD 21.

Referring now to FIGS. 18 and 19, modifications of the driving methodare described.

According to the driving method described above, the exposure times forthe short storage, the medium storage, and the long storage aresubstantially uniform and are repeated over the light reception periodof one frame. However, it is possible to drive an imaging device 1 insuch a manner that the exposure times for the long storage, the mediumstorage, and the short storage become longer in a later stage in thelight reception period of one frame.

FIG. 18 shows a first modification of the driving method. In FIG. 18, anexample of the exposure time for the long storage is shown. In thisexample, the exposure time becomes longer logarithmically as the lightreception period of one frame elapses.

FIG. 19 shows a driving method that does not involve the anti-bloominggate 23, as a second modification of the driving method. In FIG. 19, anexample of the exposure time for the long storage is shown. In thisexample, the exposure time becomes longer logarithmically as the lightreception period of one frame elapses.

As described above, even if the cycle of repeating the exposure time isnot substantially the same in an imaging device 1, HDR combining can beperformed as long as the exposure ratio after accumulation is constantamong the short storage, the medium storage, and the long storage. Also,even if the exposure ratio after accumulation varies, HDR combining isperformed with a corrected exposure ratio, so that the influence on theresultant HDR image can be reduced. For example, a more preferable HDRimage can be obtained, if some other effect that is more beneficial thanits influence has been achieved.

For example, as shown in FIGS. 18 and 19, an imaging device 1 can employa driving method by which the exposure ratio is constant while theinterval extends logarithmically (this method will be hereinafterreferred to as the nonlinear burst driving, where appropriate).

If a high-speed electronic shutter is used in a conventional imagingdevice that performs readout control only once for a frame, blurring ofeach moving object is eliminated, and the image appears sill like astill image. However, in a case where the frame rate is 30 fps, theresultant image is a non-smooth image that looks like cutoff animation,with images of approximately 1/30 s missing, unless the frame rate isincreased. Particularly, in a case where the reproduction framefrequency is low, the resultant image becomes unpleasant to the eye.Moreover, to perform a process equivalent to a high-speed process atquadruple speed (=240 fps) so as to eliminate the feeling of cutoffanimation in a today's television receiver, the speed of the imagingdevice needs to be four times higher, which requires an enormousincrease in power consumption.

To counter this, the nonlinear burst driving in which storage times areallocated so that logarithmic distribution in the temporal axis isachieved should be effective for a conventional electronic shutter thatcannot achieve both smoothness and sharpness by performing exposure onlyat the last one moment of one frame. With this, exposure control similarto the logarithmic response characteristics of the human eye isperformed, and thus, an electronic shutter that can achieve bothsmoothness and sharpness without blurring of a moving object can beobtained. That is, through the nonlinear burst distribution driving, thesame logarithmic sensitivity characteristics as the responsecharacteristics of the human eye can be achieved, and a moving imagethat can be reproduced smoothly relative to the moving object (smoothand sharp reproduction) can be captured.

It should be noted that an imaging device 1 including pixels 11 of anyof the above described examples can be used in various kinds ofelectronic apparatuses, such as imaging systems for digital stillcameras and digital video cameras, portable telephone devices havingimaging functions, and other apparatuses having imaging functions.

FIG. 20 is a block diagram showing an example configuration of animaging apparatus mounted in an electronic apparatus.

As shown in FIG. 20, an imaging apparatus 101 includes an optical system102, an imaging device 103, a signal processing circuit 104, a monitor105, and a memory 106, and can take still images and moving images.

The optical system 102 includes one or more lenses to guide image light(incident light) from the object to the imaging device 103, and form animage on the light receiving surface (the sensor portion) of the imagingdevice 103.

An imaging device 1 including pixels 11 of any of the above describedembodiments may be used as the imaging device 103. In the imaging device103, electrons are accumulated for a certain period of time inaccordance with an image to be formed on the light receiving surface viathe optical system 102. Then, a signal in accordance with the electronsaccumulated in the imaging device 103 is then supplied to the signalprocessing circuit 104.

The signal processing circuit 104 performs various kinds of signalprocessing on pixel signals that are output from the imaging device 103.The image (image data) obtained through the signal processing performedby the signal processing circuit 104 is supplied to and displayed on themonitor 105, or is supplied to and stored (recorded) into the memory106.

In the imaging apparatus 101 having the above described configuration,an imaging device 1 including pixels 11 of any of the above embodimentsis used, so that HDR images with a higher image quality can be taken. Itshould be noted that the present technology may also be embodied in theconfigurations described below.

(1)

An imaging device including:

a pixel region in which pixels are arranged, the pixels each including aphotoelectric conversion unit that converts incident light into electriccharges through electric conversion and stores the electric charges, andtwo or more charge storage units that store the electric chargestransferred from the photoelectric conversion unit; and

a drive unit that drives each pixel to cause the photoelectricconversion unit to repeatedly transfer electric charges with differentexposure times to the two or more charge storage units during the lightreception period of one frame.

(2)

The imaging device of (1), in which the two or more charge storage unitshave different possible charge storage capacities.

(3)

The imaging device of (1) or (2), in which an electric charge with along exposure time is transferred to the charge storage unit having thesmaller charge storage capacity of the two or more charge storage units,and an electric charge with a short exposure time is transferred to thecharge storage unit having the larger charge storage capacity.

(4)

The imaging device of any of (1) to (3), further including

an anti-blooming gate that discharges electric charges overflowing fromthe photoelectric conversion unit during the exposure period for thepixel.

(5)

The imaging device of (3), in which a potential is set so that electriccharges overflowing from the photoelectric conversion unit during theexposure period for the pixel is discharged to the charge storage unithaving the smaller charge storage capacity.

(6)

The imaging device of any of (3) to (5), in which a storage unit havinga capacitor structure that extends through a diffusion junction is usedas the charge storage unit having the larger charge storage capacity.

(7)

The imaging device of any of (3) to (6), in which a storage unit havinga light-shielded photodiode structure is used as the charge storage unithaving the smaller charge storage capacity.

(8)

The imaging device of any of (1) to (7), further including

a charge-voltage conversion unit that converts an electric chargegenerated in the photoelectric conversion unit into a voltage,

in which

electric charges are transferred from the two or more charge storageunits to the charge-voltage conversion unit that is shared, and

the two or more charge storage units share the charge-voltage conversionunit and components in later stages.

(9)

The imaging device of any of (1) to (8), in which the drive unitperforms driving so that the exposure time for the electric charge to betransferred to each of the two or more charge storage units issubstantially the same in each of the charge storage units during thelight reception period of one frame.

(10)

The imaging device of any of (1) to (9), in which the drive unitperforms driving so that the exposure time for the electric charge to betransferred to each of the two or more charge storage units issubstantially the same over the light reception period of one frame.

(11)

The imaging device of any of (1) to (9), in which the drive unitperforms driving so that the exposure time for the electric charge to betransferred to each of the two or more charge storage units becomeslonger as the light reception period of one frame elapses.

(12)

A method of driving an imaging device that includes: a pixel region inwhich pixels are arranged, the pixels each including a photoelectricconversion unit that converts incident light into electric chargesthrough electric conversion and stores the electric charges, and two ormore charge storage units that store the electric charges transferredfrom the photoelectric conversion unit; and a drive unit that drives thepixels,

the method including

repeatedly transferring electric charges with different exposure timesfrom the photoelectric conversion unit to the two or more charge storageunits during the light reception period of one frame, the drive unitcausing the photoelectric conversion unit to repeatedly transferelectric charges.

(13)

An electronic apparatus including

an imaging device including:

a pixel region in which pixels are arranged, the pixels each including aphotoelectric conversion unit that converts incident light into electriccharges through electric conversion and stores the electric charges, andtwo or more charge storage units that store the electric chargestransferred from the photoelectric conversion unit; and

a drive unit that drives each pixel to cause the photoelectricconversion unit to repeatedly transfer electric charges with differentexposure times to the two or more charge storage units during the lightreception period of one frame.

It should be noted that this embodiment is not limited to the abovedescribed embodiments, and various modifications may be made to themwithout departing from the scope of the present disclosure.

REFERENCE SIGNS LIST

-   1 Imaging device-   2 Pixel region-   3 Vertical drive circuit-   4 Column signal processing circuit-   5 Horizontal drive circuit-   6 Output circuit-   7 Control circuit-   11 Pixel-   21 PD-   22 Charge readout path-   23 Anti-blooming gate-   31 Transfer gate-   32 Charge storage gate-   33 Readout gate-   34 FD unit-   35 Storage capacitor-   36 Amplification transistor-   37 Select transistor-   38 Reset transistor-   41 to 43 Gate electrode-   44 and 45 Through electrode-   51 Gate electrode-   52 Through electrode-   61 Light shielding film-   62 Opening-   71 Capacitor-   72 Light-shielded HAD-   81 On-chip lens-   82 Charge storage unit-   83 Reset drain

1. An imaging device comprising: a pixel region in which a plurality ofpixels are arranged, the pixels each including a photoelectricconversion unit configured to convert incident light into electriccharges through electric conversion and store the electric charges, andtwo or more charge storage units configured to store the electriccharges transferred from the photoelectric conversion unit; and a driveunit configured to drive each pixel to cause the photoelectricconversion unit to repeatedly transfer electric charges with differentexposure times to the two or more charge storage units during a lightreception period of one frame.
 2. The imaging device according to claim1, wherein the two or more charge storage units have different possiblecharge storage capacities.
 3. The imaging device according to claim 2,wherein an electric charge with a long exposure time is transferred tothe charge storage unit having the smaller charge storage capacity ofthe two or more charge storage units, and an electric charge with ashort exposure time is transferred to the charge storage unit having thelarger charge storage capacity.
 4. The imaging device according to claim1, further comprising an anti-blooming gate configured to dischargeelectric charges overflowing from the photoelectric conversion unitduring an exposure period for the pixel.
 5. The imaging device accordingto claim 3, wherein a potential is set so that electric chargesoverflowing from the photoelectric conversion unit during an exposureperiod for the pixel is discharged to the charge storage unit having thesmaller charge storage capacity.
 6. The imaging device according toclaim 3, wherein a storage unit having a capacitor structure thatextends through a diffusion junction is used as the charge storage unithaving the larger charge storage capacity.
 7. The imaging deviceaccording to claim 3, wherein a storage unit having a light-shieldedphotodiode structure is used as the charge storage unit having thesmaller charge storage capacity.
 8. The imaging device according toclaim 1, further comprising a charge-voltage conversion unit configuredto convert an electric charge generated in the photoelectric conversionunit into a voltage, wherein electric charges are transferred from thetwo or more charge storage units to the charge-voltage conversion unitthat is shared, and the two or more charge storage units share thecharge-voltage conversion unit and components in later stage.
 9. Theimaging device according to claim 1, wherein the drive unit performsdriving so that an exposure time for an electric charge to betransferred to each of the two or more charge storage units issubstantially the same in each of the charge storage units during thelight reception period of one frame.
 10. The imaging device according toclaim 1, wherein the drive unit performs driving so that an exposuretime for an electric charge to be transferred to each of the two or morecharge storage units is substantially the same over the light receptionperiod of one frame.
 11. The imaging device according to claim 1,wherein the drive unit performs driving so that an exposure time for anelectric charge to be transferred to each of the two or more chargestorage units becomes longer as the light reception period of one frameelapses.
 12. A method of driving an imaging device that includes: apixel region in which a plurality of pixels are arranged, the pixelseach including a photoelectric conversion unit configured to convertincident light into electric charges through electric conversion andstores the electric charges, and two or more charge storage unitsconfigured to store the electric charges transferred from thephotoelectric conversion unit; and a drive unit configured to drive thepixels, the method comprising repeatedly transferring electric chargeswith different exposure times from the photoelectric conversion unit tothe two or more charge storage units during a light reception period ofone frame, the drive unit causing the photoelectric conversion unit torepeatedly transfer electric charges.
 13. An electronic apparatuscomprising an imaging device including: a pixel region in which aplurality of pixels are arranged, the pixels each including aphotoelectric conversion unit configured to convert incident light intoelectric charges through electric conversion and store the electriccharges, and two or more charge storage units configured to store theelectric charges transferred from the photoelectric conversion unit; anda drive unit configured to drive each pixel to cause the photoelectricconversion unit to repeatedly transfer electric charges with differentexposure times to the two or more charge storage units during a lightreception period of one frame.